FAT-ABSORBING FUNCTION OF ALIMENTARY TRACT OF KING SALMON. 1 73 



SUMMARY. 



In summarizing the results presented in the preceding pages the salient facts may 

 be mentioned as follows: 



1. Fats are absorbed through the columnar epithelium of all portions of the 

 alimentary tract of the king salmon. 



2. The primary function of the numerous pyloric coeca is that of fat absorption. 

 Probably the larger portion of the fats of the food of the salmon are absorbed by way 

 of these organs. 



3. The intestine is a region of active fat absorption. The power of the intestinal 

 epithelium to take up fat is similar to that of the pyloric caca. 



4. The salmon stomach is also a fat-absorbing organ. Fat is absorbed by both the 

 cardiac and the pyloric types of columnar epithelium. 



5. The microscopic indications are that the fats pass through the outer portions 

 of the columnar epithelial cells in a dissociated form and that resynthesis takes place 

 within the cell, thus accounting for the numerous large fat droplets present in the cells 

 during active fat absorption. 



DESCRIPTION OF FIGURES. 



The following list of figures was drawn for me by Mr. George T. Kline, biological 

 artist of the University of Missouri. It is difficult, especially in low magnification 

 figures, to represent the exact amount of fat in the plain of a cross section. But the 

 relative amount is represented and by the aid of a camera lucida. In the figures of 

 high magnification the exact size and location of every droplet has been followed with 

 the greatest care. Figures 5 and 6 represent preparations in which the fat was stained 

 by osmic acid. All other figures are from sections prepared from frozen section stained 

 with scarlet red. 



Plate XII. 



Fig. I. — Showing fat absorption by the epithelium of the pyloric portion of the salmon stomach. 

 This fish was a young specimen from the McCloud River, Baird, Cal. It was fed olive oil 20 hours 

 before preparation. The superficial epithelium is crowded with fat. Other portions of the same section 

 show even a greater loading, extending down to the cells of the bottoms of the crypts. Traces of fat 

 liposomes are noticed in the lymph vessels in the folds. Fat-fed salmon no. 88. Camera lucida outlines. 

 Magnification, Leitz ocular i, objective 7. 



Fig. 2. — Transverse section showing fat absorption in the posterior loop of the intestine in a fat -fed 

 salmon from Brookdale, Cal. This young specimen had been fed 18 hoiu-s previous to killing. Fat is 

 crowded into the cylindrical epithelial cells, and has passed in considerable quantity into the spaces of 

 the tunica propria. The folding of the intestinal mucous epithelium is relatively simple in young 

 salmon of this age. Brookdale salmon no. 45, Camera lucida outlines. Magnification, Leitz ocular 3, 

 objective 3 with the lower lens removed. 



Pl.^te XIII. 



Fig. 3 . — Showing fat absorption in a transverse section through the intestine of fat-fed salmon no. 45. 

 This figure represents with larger magnification one of the folds show-n in figure 2. The general outlines 

 of the figure are drawn with camera lucida. The fat of the epithelial cells was laid in primarily from 

 this section, but in part from a comparative study of other sections. The fat-bearing portion of the 

 epithelium between the two goblet cells to the left was torn in the section, and this portion is all recon- 

 19371°— vol 33—15 12 



